In printing methods of this sort as in an ordinary rotary printing method, as shown e. g., in JP 2005-335145 A a web of paper for rotary press printed on by an ink jet printer is fed to travel at a predetermined speed unidirectionally from a paper feeder unit to a paper takeup unit.
In the printing methods of this sort, for a variety of reasons such as ending of printing data, division of printing data for each of small numbers of copies, a mechanical reason as adjustment, checking of a printing state and operational convenience, there may en route be temporary halts of or suspensions from continuous printing operation, the printing operation being subsequently reinitiated.
In that method in which a web of paper in course of printing is fed to travel at a fixed speed, the web of paper caused to halt on the way travels up over a certain distance, leaving a portion left blank due to inertia of the printing system. And, when printing is reinitiated, the printing operation is initiated on a portion of paper following the blank portion of paper produced when printing is temporarily halted en route, with the result that such blank portions are mixed as NG portions of printed paper in a paper takeup roll downstream in the printing system.
Consequently, in conventional digital printing methods of this sort the problem has come up that if a printing operation after it is temporarily halted en route therein is reinitiated, in a process of post-processing a takeup roll of printed paper, steps of treating NG portions of printed paper become complicated and troublesome. Further, where a printing speed exceeding 200 m/min is available in the latest printing method, the problem has arisen that a blank portion of printed paper produced when printing is halted temporarily en route is elongated, giving rise to an increase in the amount of broke or waste of paper.
In view of the foregoing problems, it is an object of the present invention to provide a digital printing method as well as a system therefor which, if a continuous printing operation after it is halted temporarily en route is reinitiated, is capable of printing without producing waste of paper due to a portion left blank on a web of paper for rotary press.